The present invention relates to a sound field correcting method of correcting a sound field characteristic in an audio system.
The audio system is required to produce the proper sound field space that can give a presence. In the prior art, the sound field correcting method in the audio system disclosed in the Japanese Utility Model Application Publication (KOKAI) Hei 6-13292 has been known.
The audio system in the prior art is the so-called multi-channel audio system having loudspeakers for a plurality of channels, and an equalizer for adjusting frequency characteristics of input audio signals and delay circuits for delaying the audio signals output from the equalizer are provided, and then outputs of the delay circuits on respective channels are supplied to respective loudspeakers on a plurality of channels.
Also, in order to correct the sound field characteristic, there are provided a pink noise generator, an impulse generator, a selector circuit, a microphone used to measure the reproduced sound being reproduced by the loudspeakers, a frequency analyzing means, and a delay time calculating means. Then, a pink noise generated by the pink noise generator is supplied to the equalizer via the selector circuit on respective channels, and an impulse signal generated by the impulse generator is directly supplied to the loudspeakers on respective channels via the selector circuit.
Upon correcting the phase characteristic of the sound field space, propagation delay times of the impulse sound from the loudspeakers to a listening position are measured by measuring the impulse sound reproduced via the loudspeakers by the microphone while supplying directly the impulse signal from the above impulse generator to the loudspeakers and then analyzing the measured signals by using the delay time calculating means.
In other words, the propagation delay times of respective impulse sounds are measured by directly supplying the impulse signal to respective loudspeakers and calculating time differences from points of time when respective impulse signals are supplied to respective loudspeakers to points of time when respective impulse sounds being reproduced by every loudspeaker come up to the microphone by using the delay time calculating means. Thus, the phase characteristic of the sound field space can be corrected by adjusting the delay times of respective channels of the above delay circuit based on respective measured propagation delay times.
Also, upon correcting the frequency characteristic of the sound field space, the pink noise is supplied from the pink noise generator to the equalizer on respective channels and then respective reproduced sounds of the pink noise reproduced via respective loudspeakers are measured by the microphone, and then frequency characteristics of the measured signals are analyzed by the frequency analyzing means. Thus, the frequency characteristic of the sound field space can be corrected by feedback-controlling the frequency characteristics of the equalizers on respective channels based on the analyzed results.
However, in the sound field correcting method in the audio system in the prior art, since levels (sound pressures) of respective reproduced sounds reproduced by a plurality of loudspeakers are not adjusted between the channels, such a phenomenon occurs that levels of the reproduced sounds reproduced by a low frequency band exclusively reproducing loudspeaker and all frequency band reproducing loudspeakers are enhanced in the low frequency when the sound field correction of the multi-channel audio system, that has the low frequency band exclusively reproducing loudspeaker such as a subwoofer and the all frequency band reproducing loudspeakers which can reproduce the audio signals over the overall audio frequency band, for example, is carried out. Therefore, the problems are caused such that the faithful audio reproduction cannot be achieved and thus this gives the unpleasant feeling to the listener, etc.